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Chapter 1) 7SR23 DAD Description Of Operation
©2013 Siemens Protection Devices Limited
Chapter 1 Page 27 of 36
5.2
Sustained Fault, CB Fail & CB Position Monitoring
The Sustained Fault Monitor (87/50SFM) feature can be used where either dedicated CB fail protection is not
fitted and/or where the location of the protection CTs may introduce operational constraints.
If after operation of the differential protection the fault remains uncleared this is due to either a CB fail condition or
because the fault has occurred in a protection blind spot created by the position of the CTs. This function can
identify and differentiate between a failed CB and a blind spot fault – see Chapter 7, Applications Guide.
When selected to ‘Enabled’ the 87SFM Delay starts after operation of the 87/50-1 protection, when the DTL
elapses it indicates that the fault remains un-cleared.
87SFM functionality is enhanced where CB status information is available either over the 61850 bus or from CB
auxiliary switches wired to binary inputs of the relay. When enabled by the 87/50BF (differential current CB fail )
feature a CB fail condition can be determined and the faulted circuit breaker(s) can be identified.
The 87/50SFM feature will pick up where 87/50 is Enabled, 87/50SFM is Enabled, an 87/50-n element has
operated and both the ‘Inhibit 87/50SFM and CT50 have not operated.
Outputs can be mapped to any combination of output contacts or LEDs, outputs are available from:
87/50SFM
where the 87SFM DTL has elapsed.
87/50BF
output is issued where CB status monitoring is available and one of the monitored CBs does
not indicate open i.e. a CB fail condition has been detected.
CBn Cct Close Alarm
output is issued to identify the failed CB where CB status monitoring is available
and the CB fail condition above is detected.
87/50BF Blind Spot
output is issued where CB status is available and all CBs are open after a
sustained differential current is detected.
Operation of the Sustained Fault Monitor function can be inhibited from:
Inhibit 87SFM
A binary or virtual input.
CT50
Operation of the CT Supervision elements
&
Inhibit 87/50SFM
87/50SFM Pickup
CT50
87/50SFM
87/50SFM Delay
CB1 Cct Close
CB2 Cct Close
CB
n
Cct Close
CB1 Cct Close Alarm
CB2 Cct Close Alarm
CB
n
Cct Close Alarm
87/50BF
Disabled
87/50BF
87/50BF Blind Spot
1
CB3 Cct Close
CB3 Cct Close Alarm
&
&
Enabled
&
&
&
&
&
87/50-1 Operate
1
87/50-2 Operate
87/50SFM
Disabled
Enabled
87/50 Enabled
Figure 5-2 Logic Diagram: 87/50SFM and 87/50BF
Summary of Contents for 7SR23 DAD
Page 1: ...Answers for energy 7SR23 DAD High Impedance Protection Relay Reyrolle Protection Devices ...
Page 2: ......
Page 4: ...7SR23 DAD Contents 2013 Siemens Protection Devices Limited ...
Page 60: ...Chapter 3 7SR23 DAD Performance Specification 2013 Siemens Protection Devices Limited ...
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